The present invention comprises a new and distinct cultivar of calla lily, botanically known as Zantedeschia sprengeri and hereinafter referred to by the cultivar name ‘Helvetia’.
‘Helvetia’ is a product of a planned breeding program, which had the objective of creating Zantedeschia hybrids for pot flower production in a wide range of colors with a large, classic flower shape. The breeding program began in 1989, and the new cultivar is a seedling selected from the crossing of a Zantedeschia sprengeri selection referred to as Z030636 (female parent, unpatented) with Zantedeschia sprengeri ‘Swan Lake’ (male parent, U.S. Plant Pat. No. 15,664). ‘Helvetia’ was selected in 2008 by the inventor in 't Zand, The Netherlands as one flowering plant within the progeny of the stated cross.
The first act of asexual reproduction of ‘Helvetia’ by tissue culture was performed by the inventor in September of 2010 in 't Zand, The Netherlands. Subsequent asexual reproductions by tissue culture at the same location have demonstrated that the combination of characteristics as herein disclosed for the new cultivar are retained and reproduced true to type through successive generations of asexual reproduction.
The following observations, measurements and comparisons describe plants grown in 14 cm pots in 't Zand, The Netherlands under greenhouse conditions, which approximate those generally used in horticultural practice. Color references are made to The 2001 R.H.S. Colour Chart of The Royal Horticultural Society of London, except where general color terms of ordinary significance are used.
The present invention has not been evaluated under all possible environmental conditions. The phenotype may vary with variations in environment without a change in the genotype of the plant.
The following traits have been repeatedly observed and determined to be basic characteristics of ‘Helvetia’ which, in combination, distinguish this calla lily as a new and distinct cultivar:                1. White-colored spathe with no pink blush color present;        2. Green leaves with a few linear white spots; and        3. High inflorescence production.        
Further, when compared to calla lily plant named ‘Captain Ventura’ (U.S. Plant Pat. No. 21,245), ‘Captain Ventura’ has a mature outer surface spathe color that varies between White Group RHS 155C and Green-White Group RHS 157D with a Green Group RHS 143A outer tip, whereas the upper surface spathe color of ‘Helvetia’ varies between White Group RHS 155A and 155D.
Table 1 provides similarities and differences of ‘Helvetia’ to its parents, Zantedeschia sprengeri selection Z030636 and Zantedeschia sprengeri ‘Swan Lake’.
TABLE 1‘Helvetia’SimilaritiesDifferencesZ030636Spathe colorAbsence of pink blushcolor in spatheSpathe shapePlant height‘Swan Lake’Absence of pink blush color Spathe shapein spathe Number of inflorescencesSpathe colorPlant height